This section introduces aspects that may be helpful to facilitating a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light. The statements of this section are not to be understood as admissions about what is in the prior art or what is not in the prior art.
Polarization splitters split polarized light into transverse electric (TE) and transverse magnetic (TM) polarized light. Mach-Zehnder interferometer type polarization splitters may be used in a number of optical telecommunication applications, such as polarization diversity receivers, polarization shift keying and polarization diversity multiplexing. For broadest applicability, it would be desirable for the polarization splitter to be operable over a wide range of wavelengths, for example, the entire C-band wavelength range. Providing such wavelength insensitivity in a low-cost and compact designed apparatus has been problematic, however. For instance, some previous efforts require additional processing steps to selectively deposit metal layers on or near one of the waveguides to induce or change the birefringent properties of the waveguide and thereby achieve a split in polarized light. In addition to requiring additional processing steps, such designs can have substantial insertion losses. Other efforts require the deposition of a stress-inducing material in the vicinity of one waveguide to induce or change the birefringent properties of the waveguide and thereby achieve the desired split in polarized light. Again, this requires additional processing steps to place the stress-inducing material near the waveguide. Yet other efforts require nano-lithography to create very small features. Again, this requires special processing steps and equipment.